1. Field of the Invention
The present invention relates to an ink viscosity measuring device, and an ink viscosity measurement method and apparatus, for a cardboard sheet printing apparatus.
2. Prior Art
After being pasted together by a corrugator (not shown), cardboard sheets are ruled and cut to desired dimensions, and are then printed, scored and stamped out by means of a cardboard sheet boxing machine (not shown). For the most part, flexo printing using water-soluble flexo inks and printer-slotter printing using glycol type printer-slotter inks are used in the printing of cardboard sheets.
As shown in FIG. 22, the printing unit 1 of a flexo printing apparatus in a cardboard sheet boxing machine comprises: a printing cylinder 2 around which a printing plate (not shown) is wrapped, a pressing roll 3 which is installed facing the printing cylinder 2 with a paper line PL interposed between the two rolls, an ink roll 4 and a wringing roll 5 which are installed so as to face the printing cylinder 2, and an ink collecting area A which is formed between the two rolls 4 and 5, and an ink collecting area A which is formed between the two rolls 4 and 5. An anilox roll in which fine engraving is formed is usually used as the ink roll 4. The wringing roll 5 performs a wringing action that causes the formation of an appropriate ink coating film on the surface of the ink roll 4. Accordingly, a rubber roll system is which a hard rubber is wrapped around the roll surface is most commonly used as the wringing roll 5. However, a so-called chamber blade system in which wringing of the ink is performed by pressing a blade against the ink roll 4 may also be used. The supply of ink to the ink roll 4 and wringing roll 5 in the ink collecting area A is accomplished so that ink in an ink tank 8 installed inside the printing unit 1 or near the printing unit 1 is drawn upward by an ink pump 7 from an ink suction port 9, this ink passes through an ink supply passage 10 and is supplied from an ink supply port 11. Here, the ink is wrung to an appropriate amount by the ink roll 4 and wringing roll 5, and is transferred onto the printing plate wrapped around the printing cylinder 2. Furthermore, the excess ink flows out from both end of the ink roll 4 and wringing roll 5 (with respect to the axial direction of the rolls); then, this ink is received by ink pans 6 installed at the ends of the ink roll 4 and wringing roll 5 and eventually recovered in the ink tank 8 via an ink return passage 12 and ink return port 13.
Since flexo inks are quick-drying inks, it has been necessary in flexo printing apparatus to cause the constant circulation of a large amount of ink in order to reduce the effects of drying of the ink in the ink apparatus and ink passages inside the printing apparatus. Furthermore, since such inks are water-soluble, there have been instances in which the ink viscosity rises as a result of the evaporation of the water content of the ink during ink circulation. For example, there have been instances in which the water content of the ink is discharged into the air as a result of long-term circulation of the ink, so that the viscosity of the ink rises, instances in which the water content of the ink is evaporated by the heat of friction between the ink roll 4 and the wringing roll 5 when the ink is wrung by the ink roll 4 and wringing roll 5, so that the viscosity of the ink rises, and instances in which the water content of the ink is evaporated by the action of the mechanically generated heat of the ink pump 7 on the circulating ink, so that the viscosity of the ink rises.
If the viscosity of the ink rises, differences in the relative lightness and darkness of printing are generated according to the cardboard sheets when printing is performed on such sheets, so that unsatisfactory printing results. In addition, since the cardboard sheets are coated with more ink than is necessary, ink consumption is conspicuous so that ink loss results. Furthermore, if the ink viscosity rises, the fluidity of the ink drops, so that large quantities of ink remain in the ink passages when the ink is replaced, thus resulting in deterioration in the ink recovery rate. This also leads to ink loss. Moreover, since large quantities of ink remain in the ink passages, the ink cleaning efficiency also drops, so that more time is required for cleaning. Consequently, large quantities of cleaning waste liquid are discharged, and ink that cannot be cleaned away solidifies and is deposited in the ink passages, so that the subsequent flow-through of ink is hindered. Meanwhile, since flexo printing is suited for large-quantity production, such printing is used in the production of large quantities of sheets. However, in cases where flexo printing is used in such production, the viscosity of the ink varies during production so that there is sometimes a conspicuous difference in the relative lightness and darkness of printing between the printing that is performed initially and the final printing. In order to prevent the variation in the ink viscosity that causes such unsatisfactory printing, the operator periodically measures the viscosity of the ink and controls the ink viscosity.
For example, a measuring instrument 53 known as a Zahn cup No. 4 such as that shown in FIG. 21 is generally used in ink viscosity control. As shown in FIG. 21A, this Zahn cup 53 is placed in the ink tank 8, and after the interior of the Zahn cup 53 is filled with ink, the operator grasps the handle 53b of the Zahn cup 53, and quickly draws the Zahn cup 53 upward out of the ink tank 8 as shown in FIG. 21B. An ink escape hole 53a is formed in the bottom of the Zahn cup 53, and when the Zahn cup 53 is drawn upward out of the ink tank 8, ink continuously drops from this escape hole 53a. When the ink inside the Zahn cup 53 is eventually exhausted, then ink no longer drops from the Zahn cup 53, as shown in FIG. 21C. Since the volume of the Zahn cup 53 and the size of the escape hole 53a are known, the rate at which the ink drops is a fixed rate that corresponds to the viscosity of the ink. Accordingly, the viscosity of the ink can be ascertained from the time that is required for the ink to drop. Specifically, in the case of a lower ink viscosity, the dropping of the ink is completed more quickly, while a higher ink viscosity requires a longer time for completion of the dropping of the ink. Accordingly, the ink viscosity is measured by the time required for the dropping of the ink from the Zahn cup 53 to cease after the Zahn cup 53 is drawn upward out of the ink tank 8, i.e., the dropping time of the ink when there is a change from the state shown in FIG. 21B to the state shown in FIG. 21C. As one example, assuming that an ink dropping time (according to the Zahn cup 53) of 10 seconds represents the most suitable ink viscosity for the printing of a certain order, it is judged that the ink viscosity is higher than the optimal value of the ink viscosity for the printing of the order in cases where the ink dropping time is longer than 10 seconds. Conversely, in cases where the ink dropping time is shorter than 10 seconds, it is judged that the ink viscosity is lower than the above-described optimal value. Then, the operator ascertains the viscosity of the ink on the basis of the measurement results. In cases where the viscosity of the ink is too high, the operator supplies an appropriate amount of a diluent liquid such as water, etc. to the ink tank 8 on the basis of past experience. In cases where the viscosity of the ink is too low, the operator supplies the ink stock liquid to the ink tank 8. The viscosity of the ink is adjusted by repeating this process.
However, in cases where the viscosity of the ink is measured by means of a Zahn cup 53 as described above, the measurement is performed visually by the operator, and thus depends greatly on the skill of the operator, so that the measured values of the ink viscosity often differ from measurement to measurement. Furthermore, in order to obtain an accurate grasp of the ink viscosity, measurements must be repeated a number of times, and the correct viscosity must be calculated from the mean value of the measurement results. Since the viscosity of the ink cannot be accurately measured unless a number of measurements are performed as described above, measurement of the ink viscosity takes time, and the measurement work is bothersome. Furthermore, the Zahn cup 53 must be washed for each type of ink used, so that the operator is burdened by the work that is required. Moreover, since the standards of judgment used in measurement vary depending upon the operator, the measured viscosity of the ink varies according to the operator that performs the measurement, so that even in cases where printing of the same order is performed, it is difficult to obtain the same ink viscosity if the ink viscosity is measured by a different operator, so that printing in which the shade is different may be performed even in the case of printed matter of the same order.
Furthermore, measurement of the ink viscosity by means of a Zahn cup 53 is performed arbitrarily by the operator with an irregular timing according to breaks in the work. Accordingly, for example, accurate viscosity control cannot be achieved even in the same order, and in cases where the operator is busy during production, or in cases where the operator simply forgets to perform measurements, differences in the relative lightness and darkness of printing may result in unsatisfactory printing. Moreover, the supply of a diluent liquid or ink stock liquid for the purpose of adjusting the ink viscosity after the ink viscosity measurement results have been received depends greatly on the experience and intuition of the operator, so that the work is difficult for inexperienced operators.
In regard to ink viscosity measurements that do not use a Zahn cup 53 of the type described above, there are methods that perform ink viscosity measurements using special ink viscosity measuring devices. For example, such methods are described in Japanese Patent Application Laid-Open (Kokai) Nos. H10-264358, H6-213794, H8-230160, etc. However, the ink viscosity measuring devices disclosed in these patents are large and expensive. Furthermore, the ink viscosity cannot be measured in the ink circulation passages, so that direct measurement of the ink viscosity during printing is impossible. Furthermore, there is also a method (disclosed in Japanese Patent Application Laid-Open (Kokai) No. H8-323961) in which the ink viscosity is measured using special ink viscosity measuring devices in the ink passages inside the printing apparatus. However, in the case of these ink viscosity measuring devices, a spring mechanism used to measure the rotational torque of the viscosity measuring element is installed between the viscosity measuring element and the driving part of this element. As a result, the apparatus is relatively large and complicated, and there are many restrictions on the place of installation. Moreover, ink recovery and cleaning must be performed each time that the type of ink being used is changed. However, in the case of the respective ink viscosity measuring devices disclosed above, the ink circulation passages inside the ink viscosity measuring device are complex, so that ink recovery and cleaning cannot be performed simultaneously with ink recovery and cleaning in the ink circulation passages inside the printing apparatus.
The object of the present invention is to eliminate complicated work on the part of the operator by using a compact, simple and inexpensive device to perform accurate measurements of the viscosity of the ink flowing through ink passages during printing or ink preparation, and also to eliminate unsatisfactory printing caused by errors in the measurement of the ink viscosity due to insufficient experience on the part of the operator or due to the operator forgetting to measure the ink viscosity as a result of being pressed by work or by human errors in the adjustment of the ink viscosity.
In order to solve the above-described problems and achieve the object, the present invention provides an ink viscosity measuring device for a printing apparatus that comprises: a printing cylinder, a pressing member, an ink roll, a wringing member which faces the ink roll in a tightly adhering manner and forms an ink collecting area between the wringing member and the ink roll, an ink circulation passage which supplies ink to the ink collecting area and recovers the ink, and an ink tank which communicates with the ink circulation passage and functions as a supply source and recovery source for the ink; and in the printing apparatus, ink in the ink collecting area is transferred to the printing cylinder via the ink roll and printed on sheets that pass between the printing cylinder and the pressing member; wherein the ink viscosity measuring device comprises:
a rotating body which is disposed inside the ink circulation passage so that the rotating body can freely rotate;
electrical rotation-imparting means which are disposed outside the ink circulation passage, magnetically coupled to the rotating body, and imparts rotation to the rotating body;
a load current value detection means which detects changes in a load current value that occurs upon changes in a viscosity of ink that contacts the rotating body when rotation is imparted to the rotating body by way of passing an electric current through the rotation-imparting means;
a memory means which stores the load current values that correspond to respective changes in the viscosity value of the ink; and
a calculating means which compares respective load current values stored in the memory means with the load current value detected by the load current value detection means and calculates an ink viscosity value at a current point in time.
Furthermore, the present invention provides an ink viscosity measuring device for a printing apparatus that comprises: a printing cylinder, a pressing member, an ink roll, a wringing member which faces the ink roll in a tightly adhering manner and forms an ink collecting area between the wringing member and the ink roll, an ink circulation passage which supplies ink to the ink collecting area and recovers the ink, and an ink tank which communicates with the ink circulation passage and functions as a supply source and recovery source for the ink; and in the printing apparatus, ink in the ink collecting area is transferred to the printing cylinder via the ink roll and printed on sheets that pass between the printing cylinder and the pressing member; and the ink viscosity measuring device comprises:
a first rotating body which is disposed inside the ink circulation passage so that the rotating body can freely rotate;
a second rotating body which is disposed outside the ink circulation passage and magnetically coupled to the first rotating body;
an electrical driving means which causes the second rotating body to rotate, and imparts rotation to the first rotating body that is magnetically coupled with the second rotating body;
a load current value detection means which detects changes in a load current value that occurs upon changes in a viscosity of ink that contacts the first rotating body when rotation is imparted to the first rotating body by way of passing an electric current through the electrical driving means;
a memory means which stores the load current values that correspond to respective changes in the viscosity value of the ink; and
a calculating means which compares respective load current values stored in the memory means with the load current value detected by the load current value detection means, and calculates an ink viscosity value at the current point in time.
The present invention further provides an ink viscosity measuring device for a printing apparatus that comprises: a printing cylinder, a pressing member, an ink roll, a wringing member which faces the ink roll in a tightly adhering manner and forms an ink collecting area between the wringing member and the ink roll, an ink circulation passage which supplies ink to the ink collecting area and recovers the ink, and an ink tank which communicates with the ink circulation passage and functions as a supply source and recovery source for the ink; and in the printing apparatus, ink in the ink collecting area is transferred to the printing cylinder via the ink roll and printed on sheets that pass between the printing cylinder and the pressing member; and the ink viscosity measuring device comprises:
a rotating body which is disposed inside the ink circulation passage so that the rotating body can freely rotate;
a magnetic field switching means which is disposed outside the ink circulation passage, magnetically coupled with the rotating body when an electric current passes through the switching means, and imparts rotation to the rotating body by way of switching of magnetic fields;
a load current value detection means which detects changes in a load current value that occurs upon changes in a viscosity of ink that contacts the rotating body when rotation is imparted to the rotating body by way of passing an electric current through the magnetic field switching means;
a memory means which stores the load current values that correspond to respective changes in the viscosity value of the ink; and
a calculating means which compares respective load current values stored in the memory means with the load current value detected by the load current value detection means and calculates an ink viscosity value at a current point in time.
The present invention further provides an ink viscosity measuring device used in a printing apparatus that comprises: a printing cylinder, a pressing member, an ink roll, a wringing member which faces the ink roll in a tightly adhering manner and forms an ink collecting area between the wringing member and the ink roll, an ink circulation passage which supplies ink to the ink collecting area and recovers the ink, and an ink tank which communicates with the ink circulation passage and functions as a supply source and recovery source for the ink; and in the printing apparatus, ink in the ink collecting area is transferred to the printing cylinder via the ink roll and printed on sheets that pass between the printing cylinder and the pressing member; and the viscosity measuring device comprises:
a rotating body which is disposed inside the ink circulation passage so that the rotating body can freely rotate;
an electric current direction switching means which is disposed outside the ink circulation passage, magnetically coupled with the rotating body when an electric current passes through the switching means, and imparts rotation to the rotating body by periodically switching a direction of the electric current;
a load current value detection means which detects changes in a load current value that occurs upon changes in a viscosity of ink that contacts the rotating body when rotation is imparted to the rotating body by way of passing an electric current through the electric current direction switching means;
a memory means which stores the load current values that correspond to respective changes in the viscosity value of the ink, and
a calculating means which compares respective load current values stored in the memory means with the load current value detected by the load current value detection means and calculates an ink viscosity value at a current point in time.
In addition, the present invention provides an ink viscosity measuring device for a printing apparatus that comprises: a printing cylinder, a pressing member, an ink roll, a wringing member which faces the ink roll in a tightly adhering manner and forms an ink collecting area between the wringing member and the ink roll, an ink circulation passage which supplies ink to the ink collecting area and recovers the ink, and an ink tank which communicates with the ink circulation passage and functions as a supply source and recovery source for the ink; and in the printing apparatus, ink in the ink collecting area is transferred to the printing cylinder via the ink roll and printed on sheets that pass between the printing cylinder and the pressing member, wherein the ink viscosity measuring device comprises:
a rotating body made of an electrical conductor and disposed inside the ink circulation passage so that the rotating body can freely rotate;
an induced current generating circuit which is disposed outside the ink circulation passage, generates a rotating magnetic field when an electric current passes through the induced current generating circuit, and imparts rotation to the rotating body by generating an induced current in the rotating body by means of the rotating magnetic field;
a load current value detection means which detects changes in a load current value that occurs upon changes in a viscosity of ink that contacts the rotating body when rotation is imparted to the rotating body by passing an electric current through the induced current generating circuit;
a memory means which stores the load current values that correspond to respective changes in the viscosity value of the ink, and
a calculating means which compares respective load current values stored in the memory means with the load current value detected by the load current value detection means and calculates an ink viscosity value at a current point in time.
The present invention further provides a printing apparatus that comprises: a printing cylinder, a pressing member, an ink roll, a wringing member which faces the ink roll in a tightly adhering manner and forms an ink collecting area between the wringing member and the ink roll, an ink circulation passage which supplies ink to the ink collecting area and recovers the ink, and an ink tank which communicates with the ink circulation passage and functions as a supply source and recovery source for the ink; and in the printing apparatus, ink in the ink collecting area is transferred to the printing cylinder via the ink roll and printed on sheets that pass between the printing cylinder and the pressing member; and the printing apparatus includes:
a rotating body which is disposed inside the ink circulation passage so that the rotating body can freely rotate;
an electric current direction switching means which is disposed outside the ink circulation passage, magnetically coupled with the rotating body when an electric current passes through the switching means, and imparts rotation to the rotating body by periodically switching a direction of the electric current;
a load current value detection means which detects changes in a load current value that occurs upon changes in a viscosity of ink that contacts the rotating body when rotation is imparted to the rotating body by way of passing an electric current through the electric current direction switching means;
a memory means which stores the load current values that correspond to respective changes in the viscosity value of the ink, and
a calculating means which compares respective load current values stored in the memory means with the load current value detected by the load current value detection means and calculates an ink viscosity value at a current point in time.
In addition, the present invention provides a printing apparatus that comprises: a printing cylinder, a pressing member, an ink roll, a wringing member which faces the ink roll in a tightly adhering manner and forms an ink collecting area between the wringing member and the ink roll, an ink circulation passage which supplies ink to the ink collecting area and recovers the ink, and an ink tank which communicates with the ink circulation passage and functions as a supply source and recovery source for the ink; and in the printing apparatus, ink in the ink collecting area is transferred to the printing cylinder via the ink roll and printed on sheets that pass between the printing cylinder and the pressing member, wherein the printing apparatus includes:
a rotating body made of an electrical conductor and disposed inside the ink circulation passage so that the rotating body can freely rotate;
an induced current generating circuit which is disposed outside the ink circulation passage, generates a rotating magnetic field when an electric current passes through the induced current generating circuit, and imparts rotation to the rotating body by generating an induced current in the rotating body by means of the rotating magnetic field;
a load current value detection means which detects changes in a load current value that occurs upon changes in a viscosity of ink that contacts the rotating body when rotation is imparted to the rotating body by passing an electric current through the induced current generating circuit;
a memory means which stores the load current values that correspond to respective changes in the viscosity value of the ink; and
a calculating means which compares respective load current values stored in the memory means with the load current value detected by the load current value detection means and calculates an ink viscosity value at a current point in time.
In order to solve the above-described problems and achieve the object, the present invention provides an ink viscosity adjusting method for a printing apparatus an ink viscosity adjusting method used in a printing apparatus that comprises: a printing cylinder, a pressing member, an ink roll, a wringing member which faces the ink roll in a tightly adhering manner and forms an ink collecting area between the wringing member and the ink roll, an ink circulation passage which supplies ink to the ink collecting area and recovers the ink, and an ink tank which communicates with the ink circulation passage and functions as a supply source and recovery source for the ink; and in the printing apparatus, ink in the ink collecting area is transferred to the printing cylinder via the ink roll and printed on sheets that pass between the printing cylinder and the pressing member, wherein the ink viscosity adjusting method comprises the steps of:
calculating a total amount of ink is by determining respective amounts of ink currently present in the ink collecting area, ink circulation passage and ink tank;
measuring a viscosity value of the ink flowing through the ink circulation passage;
comparing a measured ink viscosity value with previously prepared ink viscosity variation curves obtained for respective viscosity values, thus selecting a most appropriate ink viscosity variation curve;
calculating a proportion of an amount of added liquid that is necessary in order to obtain a target viscosity value from a selected ink viscosity variation curve; and
adjusting the ink viscosity value to the target value by supplying a calculated amount of added liquid to the ink.
Furthermore, the present invention provides an ink viscosity adjusting method used in a printing apparatus that comprises: a printing cylinder, a pressing member, an ink roll, a wringing member which faces the ink roll in a tightly adhering manner and forms an ink collecting area between the wringing member and the ink roll, an ink circulation passage which supplies ink to the ink collecting area and recovers the ink, and an ink tank which communicates with the ink circulation passage and functions as a supply source and recovery source for the ink; and in the printing apparatus, ink in the ink collecting area is transferred to the printing cylinder via the ink roll and printed on sheets that pass between the printing cylinder and the pressing member; and the ink viscosity adjusting method comprises the steps of:
comparing a measured viscosity value of ink flowing through the ink circulation passage with previously prepared ink viscosity variation curves obtained for respective viscosity values, thus selecting a most appropriate ink viscosity variation curve;
experimentally varying a viscosity value of the ink by way of supplying a known amount of added liquid to ink after the selection of the ink viscosity variation curve;
measuring again the experimentally varied ink viscosity value, then calculating a supply ratio of the known amount of added liquid from the selected ink viscosity variation curve;
calculating a total amount of ink with respect to the calculated supply ratio of the known amount of added liquid;
re-calculating the supply ratio of the added liquid with respect to the total amount of ink required in order to obtain a target viscosity value from the selected ink viscosity variation curve; and
adjusting the viscosity value of the ink to the target value by way of supplying the calculated amount of added liquid to the ink.
In order to solve the above-described problems and achieve the object, the present invention further provides a printing apparatus that comprises: a printing cylinder, a pressing member, an ink roll, a wringing member which faces the ink roll in a tightly adhering manner and forms an ink collecting area between the wringing member and the ink roll, an ink circulation passage which supplies ink to the ink collecting area and recovers the ink, and an ink tank which communicates with the ink circulation passage and functions as a supply source and recovery source for the ink; and in the printing apparatus, ink in the ink collecting area is transferred to the printing cylinder via the ink roll and printed on sheets that pass between the printing cylinder and the pressing member, wherein the printing apparatus includes:
rotating bodies which are disposed inside the ink circulation passage so that the rotating bodies can freely rotate;
electrical rotation-imparting means which are disposed outside the ink circulation passage, magnetically coupled to the rotating bodies, and impart rotation to the rotating bodies;
a load current value detection means which detects changes in a load current value that occurs upon changes in a viscosity of ink that contacts the rotating bodies when rotation is imparted to the rotating bodies by passing an electric current through the rotation-imparting means;
a memory means which stores:
the load current values that correspond to respective changes in the ink viscosity value,
information concerning ink viscosity variation curves obtained for respective ink viscosity values, and
standard viscosity values concerning an upper-limit value and a lower-limit value for the ink;
a calculating means which compares respective load current values stored in the memory means with the load current value detected by the load current value detection means and calculates an ink viscosity value at a current point in time, the calculating means further performing a calculation comparing the ink viscosity value thus obtained with the upper-limit value and lower-limit value for the ink stored in the memory means and then outputting a command to supply the added liquid;
ink amount detection means which detect respective amounts of ink present in the ink collecting area, ink circulation passage and ink tank and calculate a total amount of ink based upon detection results; and
an ink viscosity control means that:
receives an added liquid supply command from the calculating means,
selects a specified ink viscosity variation curve by way of comparing, by the calculating means, information concerning ink viscosity variation curves obtained for respective viscosity values that is stored in the memory means with a current ink viscosity value,
calculates a supply ratio of the added liquid that is necessary to obtain a target viscosity value from the selected viscosity variation curve, and
sends a command to added-liquid supply sections to supply necessary amount of added liquid to the ink in accordance with results of the calculation.
Furthermore, the present invention provides a printing apparatus that comprises: a printing cylinder, a pressing member, an ink roll, a wringing member which faces the ink roll in a tightly adhering manner and forms an ink collecting area between the wringing member and the ink roll, an ink circulation passage which supplies ink to the ink collecting area and recovers the ink, and an ink tank which communicates with the ink circulation passage and functions as a supply source and recovery source for the ink; and in the printing apparatus, ink in the ink collecting area is transferred to the printing cylinder via the ink roll and printed on sheets that pass between the printing cylinder and the pressing member; and the printing apparatus includes:
rotating bodies which are disposed inside the ink circulation passage so that the rotating bodies can freely rotate;
electrical rotation-imparting means which are disposed outside the ink circulation passage, magnetically coupled to the rotating bodies, and impart rotation to the rotating bodies;
a load current value detection means which detects changes in a load current value that occurs upon changes in a viscosity of ink that contacts the rotating bodies when rotation is imparted to the rotating bodies by way of passing an electric current through the rotation imparting means;
a memory means which stores:
the load current values that correspond to respective changes in an ink viscosity value, and
information concerning ink viscosity variation curves obtained for respective viscosity values;
a calculating means which
compares respective load current values stored in the memory means with a load current value detected by the load current value detection means and calculates the ink viscosity value at a current point in time,
compares ink viscosity value thus obtained with information concerning ink viscosity variation curves that is stored in the memory means, and
selects a most appropriate ink viscosity variation curve from the curves; and
an ink viscosity control means which
receives an added liquid supply command from the calculating means,
sends a command to added-liquid supply sections to supply a known amount of an added liquid to ink so that a viscosity of the ink is experimentally varied,
then causes a supply ratio of the known amount of added liquid to be calculated by the calculating means from the selected ink viscosity variation curve by remeasuring the ink viscosity value,
causes a total amount of ink to be calculated with respect to a calculated supply ratio of the known amount of added liquid, and
sends a command to the added-liquid supply sections to supply necessary amount of added liquid to the ink in accordance with results of the calculation;
wherein the supply ratio of the added liquid relative to the total amount of ink that is required in order to obtain the a target viscosity value is re-calculated by the calculating means from the selected ink viscosity variation curve, and a viscosity value of the ink is adjusted to the target value by supplying the calculated amount of added liquid to the ink via the added liquid supply sections.
In order to solve the above-described problems and achieve the object, the present invention provides a printing apparatus comprising a printing plate drum and a pressing drum that is disposed so as to face the printing plate drum, wherein cardboard sheets are passed between the printing plate drum and pressing drum which rotate in mutually opposite directions, thus causing specified printing to be performed on the sheets; and the printing apparatus further comprises:
an ink transfer roll which rotates in contact with a printing plate of the printing plate roll at a time of printing;
an adjustment means which makes contact with the ink transfer roll during printing and adjusts an amount of ink by wringing;
a pair of regulating members which are disposed at both ends of the ink transfer roll and adjustment means with respect to an axial direction thereof and are used to demarcate an ink collecting area between the ink transfer roll and the adjustment means;
an ink supply source which is disposed near an upper end of the ink collecting area, a specified amount of ink being stored in the ink supply source;
a first tubular body and second tubular body, opening part of one of the first tubular body and second tubular body is inserted into the ink supply source, and an opening part of another of the first tubular body and second tubular body is caused to face the ink collecting area, an ink feeding pumps being respectively connected to the first tubular body and second tubular body, and
an ink viscosity measuring instrument installed in the first tubular body so as to measure a viscosity variation of ink that is supplied to the ink collecting area that is demarcated between the ink transfer roll and adjustment means, the ink viscosity measuring instrument being comprised of:
a rotating body which is disposed inside the first tubular body so that the rotating body can freely rotate;
an electrical rotation-imparting means which is disposed outside the first tubular body, magnetically coupled to the rotating body, and imparts rotation to the rotating body;
a load current value detection means which detects changes in a load current value that accompany changes in a viscosity of ink that contacts the rotating body when rotation is imparted to the rotating body by passing an electric current through the rotation-imparting means;
a memory means which stores the load current values that correspond to respective changes in a viscosity value of the ink; and
a calculating means which compares respective load current values stored in the memory means with the load current value detected by the load current value detection means and calculates an ink viscosity value at a current point in time.
The measurement of ink viscosity by the present invention is accomplished in the manner described below. More specifically, ink drawn up from the ink tank by means of an ink pump in the ink passages enters an ink viscosity measuring instrument via the ink supply passage. A driving device installed in the ink viscosity measuring instrument is driven by a command from a driving device control section, so that a first rotating body and second rotating body installed inside the ink viscosity measuring instrument are caused to rotate synchronously at a constant rotational speed. Then, the rotational driving load current value of the driving device that causes the first rotating body (which directly contacts the ink that is flowing through) to rotate is detected by a driving device control section 23. The result of this detection is converted into an ink viscosity value by a converter 24, and the value thus obtained is displayed by an ink viscosity display device, or a warning is issued by a warning device, etc.
Likewise, in a different measurement of ink viscosity, ink drawn up from the ink tank by means of an ink pump in the ink passages enters an ink viscosity measuring instrument via the ink supply passage. Furthermore, a rotating field circuit installed in the ink viscosity measuring instrument is started by a command from a field control device, so that a rotating body installed inside the ink viscosity measuring instrument is caused to rotate at a constant rotational speed. Then, the rotational driving load current value of the rotating field circuit that causes the rotating body (which directly contacts the ink that is flowing through) to rotate is detected by the driving device control section 23. The result of this detection is converted into an ink viscosity value by a converter 24, and the value thus obtained is displayed by an ink viscosity display device, or a warning is issued by a warning device, etc.
Furthermore, in cases where the results obtained from the ink viscosity measuring device indicate that the ink viscosity has changed, the addition or supply (hereafter referred to uniformly as xe2x80x9cadditionxe2x80x9d) of water (or another diluent liquid) or the ink stock liquid is performed by the operator in accordance with an ink viscosity automatic control device, or is performed by an automatic addition device using a device that adds water (or another diluent liquid) or the ink stock liquid, etc.